/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Selection/GroupTopologySelector.h
Using the edges in the given selection as starting points, add any "edge rings" containing the edges. An edge ring is a sequence of edges that lie on opposite sides of quad-like faces, meaning faces that have four corners.
true if selection was modified (i.e., were the already selected edges part of any edge rings whose member edges were not yet all selected).
bool ExpandSelectionByEdgeRings ( [FGroupTopologySelection](API\Plugins\DynamicMesh\FGroupTopologySelection) & Selection )